SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3cbcf289803bb2d2f52b9ac98a14a7cad6f9057303e71ce18ba529e8a207df91' 
  AND token = 'AFmiOBK/xg7VQvBLfWqOpQrpZ4Ih7pmWrwrrIiDqhNw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}